In the Periphyseon Johannes Scottus Eriugena (± 810 – 877) intends to collect all available knowledge of his time about the universal subject called ‘nature’ (natura). Nature comprises both God and creation. God has created everything, but he is also the end to which all creation returns. In the Periphyseon Eriugena follows this course (of processio and reditus) of nature. His own description is also a movement towards God and in this way it is the account of a mystical ascent. But the final unification with God is beyond knowledge and words. The end to which Eriugena points lies beyond the Periphyseon, in what is not written and Eriugena explains why he has not been able to lead us all the way. Eventually he takes a position outside his own discourse by addressing his reader in the epilogue. The reader is left with the wealth of knowledge and insights that the Periphyseon has imparted, and a concomitant sense of the vastness of what lies beyond his reach.